This invention relates generally to infusion pump systems for programmed operation to deliver a selected medication to a patient, particularly of the type including an infusion pump implanted directly into the body of the patient. More specifically, this invention relates to an improved system having an implanted glucose sensor adapted for convenient sensor removal and replacement on a periodic basis.
Medication infusion pumps are generally known in the art for use in delivering a selected medication to a patient in a scheduled or preprogrammed manner. In recent years, such infusion pumps have been developed in compact form adapted for direct implantation into the body of a patient, and to deliver a specific medication such as insulin to the patient in discrete doses over an extended time period. An implanted infusion pump of this general type includes an internal medication chamber for receiving and storing a supply of the selected medication in liquid form, in combination with miniature pump means and associated programmable control means for delivering the medication to the patient in accurate and repeatable doses. For one illustrative example of an implanted medication infusion pump of this general type, see U.S. Pat. No. 4,573,994.
While implantable infusion pumps have constituted a major step forward in reliable and convenient administration of certain medications, particularly insulin for a diabetic patient, practical programmed pump operation has been limited to an open loop approach involving medication dispensing in response to anticipated patient requirements. In this regard, implanted pumps have been adapted to deliver incremental doses at predetermined times and amounts in accordance with the condition and lifestyle of a particular patient. External controller devices have been developed for altering the pump program and/or for delivering a medication dose on demand, typically via a radio telemetry connection with the implanted pump. By contrast, a closed loop system involving controlled pump operation in response to actual rather than anticipated patient medication requirements, has not been available.
In recent years, considerable research and development activity has focused upon improvements in glucose sensors for monitoring glucose concentration level in a patient fluid, such as blood. These research efforts have resulted in proposals for implanted or in vivo glucose sensors designed to provide an instantaneous reading of patient glucose concentration. For examples of proposed in vivo glucose sensors, see U.S. Pat. Nos. 4,650,547; 4,671,288; 4,781,798; 4,703,756; and 4,890,620.
The availability of implantable glucose sensors enhances the feasibility of a closed loop infusion pump system wherein operation of a medication infusion pump is responsive to actual glucose concentration measurements obtained on a continuous or frequent basis. However, the service life of an implantable glucose sensor is typically relatively short in duration, on the order of a few months, whereas current infusion pump technology provides implantable components having an operating life on the order of ten years or more. A practical system designed to accommodate periodic removal and replacement of an in vivo glucose sensor, without requiring removal or replacement of other pump system components, has not been developed.
The present invention overcomes the problems and disadvantages encountered in the prior art by providing an improved infusion pump system adapted for closed loop control in response to operation of an implanted and easily removable glucose sensor.